Sol Central Government - Question

Hi, this question is mildly pedantic but it comes up because I want to develop an Earther character in the former(?) United States and am wondering if it's lore-friendly for him to have some mild secessionist sympathies.
It's clear in the lore that the SolGov is the centralized seat of power in the Sol System, but is there any specific details anywhere on the status of the nationstates? Are they constituent blocks of the SolGov, in a voluntary or nonvoluntary federation, or has political power been centralized to such an extent that they are just a historical concept?

The Beginning_Lore page says that "Nation states as they once were have long ceased to exist." but that in of itself is up to interpretation.
Some nowadays (And, in the case of Brexit, many certainly did) argue that a nationstate under the European Union didn't exist in the same manner as one outside it, with reasons provided such as giving up sovereign fishing territories, abilities to make policy on stuff like trade, regulation, etc. But no one would genuinely argue that the "United Kingdom" as an entity did not exist as a member of the European Union. And also, as Brexit would definitively prove, there is a legal mechanism for the nationstate of the UK to leave the Union unilaterally.
In a future analogous scenario, a secessionist might not be so far outside the normal politics to be even considered fringe at all.

Another type of Union would be the US, where the 'States' are seen as differing entities but not sovereign anymore. California could not (Legally) decide to unilaterally secede from the USA. Still, though, there are secessionist movements in a lot of US states, although pretty much all of them. (Except maybe- Texas?) are pretty wacky and accompanied by other fringe political ideologies.

However, if the idea of nationstates was -so- eroded to not have any large bearing on culture or politics, and there was no mechanism to reinstate an independence, there would be very little or no justification for a character advocating for such.

As far as my interpretation goes,
"In the early 23rd century, the Terran Commonwealth, having established a great many colonies and outposts, saw a large-scale restructuring to account for its new position on the galactic stage, with the government being renamed to the Sol Central Government"

would mean that in some extent the nationstates continue to exist as something between a European and American-style union, with the ability to secede not being defined. I think with the Capital being moved off-planet, there would be serious qualms about giving over total governmental control to the SolGov, for the following reasons.

Localism - people don't like to feel like they are being ruled by a foreign cast of politicians, something shown in the Brexit Leave campaign pretty clearly

Light lag - according to https://blogs.esa.int/mex/2012/08/05/time-delay-between-mars-and-earth/ the time for a signal to go between Earth and Mars as a radio signal would be 13 minutes, 48 seconds, making a return signal take almost 28 minutes. With Bluespace tech, this of course would be much reduced, but Bluespace messaging may be very costly and not economical for all uses - Personal messages, financial data, even things like video gaming, voice calls. This would create some level of seperation between the cultures further, and might put a strain on any centralized authority which would have a need to react rapidly to a situation.

Earth is not particularly secessionist. It's also effectively under one world government with multiple devolved authorities/organisations rather than a division into nations in a political sense. States in the SCG are not directly administered by the SCG. They administer themselves. Earth is a pretty core member of the SCG and it gets quite a lot from it. It doesn't really have any reason to want to leave the SCG. There are plenty of SCG secessionists along the outer territories but for the most part the inner worlds/habitats are stable enough in terms of their position within the SCG.

I'm not too sure why a secessionist would be working for the government/on the governments exploration ship, either, to be honest.

The UK also got quite a lot out of EU membership and still voted to leave the EU, but it do take your point that such a character is somewhat unlikely. There are definitely real world analogies I think though, like "Three Percenter" militia members in the USA being veterans of the military, or to take it back to the classical era, supposedly loyal subjects like Arminius secretly being anti-roman. I'm definitely -not- implying that the backstory I was thinking of would go anywhere near being a self-antag, and the secessionist sympathies would be vague, at best. Bar-stool talk, rather than a concrete ideology.

That being said, if you or anyone else had any suggestions on how I could change background to be more believable/lore-friendly, I would definitely take them on board, be that having a different home planet, a slightly different belief or even being a different species, I would definitely take them into account. Thanks for the clarification as well!

Having such blatantly-obvious hick sentiments as, "Martians are all just space Mexicans!" etc. should probably be done away with, since I've seen you do that in a round. There are certainly people who join the US military and have gripes against the government, but outright secession is more of a fringe belief. I know a few soldiers who certainly are of the "south shall rise again!" mindset, but they generally keep that way under wraps and aren't going around yelling it over comms or at everyone they see. Ideologies like these are fine, if a bit fringe, and one doesn't need to absolutely love the government to join a uniformed service. Just keep these opinions private. Folks who want to secede aren't going around telling everyone they hate the government because that's a surefire way to be investigated and discharged.

You can have fringe beliefs, but using them to become a caricature is annoying.